package nowcoder;

/**
 * @author ：徐梦轲
 * @date ：2022/5/22 0022 22:02
 */
class ListNode {
    int val;
    ListNode next = null;

    ListNode(int val) {
        this.val = val;
    }
}

public class PalindromeList {
    public boolean chkPalindrome(ListNode A) {
        if (A == null) return false;
        if (A.next == null) return true;
        ListNode fast = A;
        ListNode slow = A;
        while (fast != null && fast.next != null) {
            fast = fast.next.next;
            slow = slow.next;
        }
        ListNode cur = slow.next;
        while (cur != null) {
            ListNode curNext = cur.next;
            cur.next = slow;
            slow = cur;
            cur = curNext;
        }
        while (A != slow) {
            if (A.val != slow.val) {
                return false;
            }
            if (A.next == slow) {
                return true;
            }
            A = A.next;
            slow = slow.next;
        }
        return true;
    }
}
